Mathieu Helie’s Complex Grid is an urban growth model based on policy rulesets designed to harness self-organisation.

The three principles Helie states as the basis of his growth model are:

1. Any size of urban growth is allowed as long as the new growth extends the boundary of the network. This ensures that the city has the economic flexibility of the medieval city and allows anyone, no matter their economic importance, to contribute to the city’s growth.
2. The network must not become so complicated that it becomes impossible to move around in order to participate in large-scale activities and a culture of congestion.
3. Streets must not grow too long without interruption in such a way that speeding and traffic accidents are encouraged.

In such a model policy rules act as instructional DNA for urban growth. The Complex Grid is part of Helie’s project to promote Emergent Urbanism.